C5.3 Flashcards
what are reversible reactions?
a reaction in which the products can react together to form the reactants
what is the symbol used in reversible reactions?
and what does it mean
⇆
means forward reaction
ie. reactants to products
what is dynamic equilibrium?
describe an analogy (if u want to die)
when the forward and backward reaction happen at the same rate - so the concs of the products and reactant stay constant (but concs don’t have to be the same)
in what system can dynamic equilibrium occur?
ONLY in a closed system (so no substances can enter or leave)
is a substance stationary if it is in dynamic equilibrium
no, the forward and backward reactions are still happening, but they both flip sides at the same ‘rate’, so it looks like nothing is changing
do reversible reactions happen by themselves?
sometimes they can be spontaneous but other times reaction conditions have to be changed (ie. heat it up, change conditions etc.)
what is the equilibrium position?
a ratio of the concs of products and the concs of reactants when dynamic equilibrium is met (the point at which there is the concs of reactants and products remain constant)
how do you calculate the effect of changing pressure on the equilibrium position?
1) calculate moles on each side
2) therefore, the position would shift to side with least moles
IN ORDER TO TRY AND GO BACK TO EQUILIBRIUM
if correct attempt question on p188 - example one
why does the equilibrium position shift in the first place?
since one of the conditions have changed, and in order to try and get the amount of products vs reactants at a dynamic equilibrium
how do you calculate the effect of changing concentration on the equilibrium position?
(as it is usually in terms of increasing the concentration of one reactant)
- the equilibrium position shifts away from that substance,
ie. if sulfuric acid is on left, equilibrium position shifts to the right
describe the concept behind the effect of changing concentration on the equilibrium position
- ultimately, this reversible reaction wants to go back to equilibrium right?
- therefore, is one (ie. product’s) concentration increases, then more product is made to counter that in order to balance both substances out
what is the effect of changing the temperature on the equilibrium position?
1) look at the enthalpy number ie. (∆H = -58kJ/mol)
if temp increases:
equilibrium shifts to the direction of the endothermic reaction
whole idea is which way would make the temperature go back to equilibrium
how would the enthalpy number look for a
(a) exothermic reaction
(b) endothermic reaction
(a) (∆H = -58kJ/mol)
MINUS NUMBER as overall heat is lost
(b) (∆H = +58kJ/mol)
POSITIVE NUMBER as overall heat is gained
